These are after-tax figures. Burtless also points out that after-transfer figures reveal the degree to which tax relief and government programs insulated lower quantiles from the recession:

The things that have become terribly expensive in the last 5 decades are the things we’ve been subsidizing: healthcare, education and real estate. Healthcare is directly subsidized through government programs, and the degree to which that makes a difference is clear here. Education transfers are outside this analysis, but all colleges are running a progressive pricing system. Redistribution mechanisms have grown dramatically in the US, but they have become far more opaque than direct government transfers.